A yaw damper, which will often be employed horizontally, is preferably used between two bogies or between a bogie and a vehicle part, in particular a rail vehicle. A wheel set is thereby prevented from leaving the rails.
Yaw dampers of this type are generally employed in railway engineering and the connecting lines in the damper which can determine the damping characteristic are either fitted in the piston of the piston part or are constructed as a by-pass in the cylinder part. Self-evidently, combinations of both constructions are possible.
With the increase in travel speeds on the railway, the demands placed upon yaw dampers are becoming higher. In particular, “stiffer” constructions are demanded. This can be effected by constructing the various components of the yaw damper with greater wall thickness and larger dimensioning. It is also possible to choose higher initial pressure of the chambers separated by the piston of the piston part, by utilizing gas primary pressure and the like to create a permanent pretension. However, such constructions make a yaw damper heavy and complicated, and operating reliability declines. Such drawbacks are particularly disadvantageous in railway engineering. For some applications, moreover, it is desirable for the stiffness of the damper to be dependent on the travel speed.
DE 19836487 discloses a so-called Nivomat, which is fitted in the wheel suspension of a vehicle and with which the level of the vehicle with respect to the road is kept constant. For this purpose, the piston rod is of hollow construction and within it moves a pin which extends from the cylinder bottom and is provided with a bore, connected to a reservoir. When the vehicle is close to ground level, this pin forms a sealing closure in the bore of the piston, so that, upon mutual displacement, pumping action is obtained via non-return valves fitted for this purpose. As soon as the piston part and the cylinder part move apart, a groove in the pin communicates with one of the chambers, whereby the pin is no longer accommodated in tight-closing arrangement in the bore of the piston part, and pumping means, as a result of fluid leaks, are no longer effective. This occurs if the desired level has been reached.
The piston part is provided in the customary manner with valves which determine the characteristic of the damping, as well as a constant which, in the case of low displacement speed or standstill of the piston part with respect to the cylinder part, provides pressure equalization of the two chambers separated by the piston part. Such a damper is not suitable for railway application as a yaw damper.
It is therefore an object of the present invention is to provide a yaw damper of simple construction, which at desired moments is sufficiently stiff and has relatively low weight.